Continuously variable transmission

ABSTRACT

A continuously variable transmission (CVT) having a main shaft configured to support and position various components of the CVT. Shift cam discs cooperate with ball-leg assemblies to shift the transmission ration of the CVT. Load cam discs, a torsion disc, rolling elements, and a hub cap shell are configured to generate axial force, transmit torque, and manage reaction forces. In one embodiment, a splined input shaft and a torsion disc having a splined bore cooperate to input torque into the variator of the CVT. Among other things, various ball axles, axle-ball combinations, and reaction force grounding configurations are disclosed. In one embodiment, a CVT having axial force generation means at both the input and output elements is disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/243,484, filed Oct. 4, 2005, which claims the benefit of U.S.Provisional Application No. 60/616,399, filed on Oct. 5, 2004. Each ofthe above-identified applications is incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates generally to transmissions, and moreparticularly to continuously variable transmissions (CVTs).

2. Description of the Related Art

There are well-known ways to achieve continuously variable ratios ofinput speed to output speed. The mechanism for adjusting an input speedfrom an output speed in a CVT is known as a variator. In a belt-typeCVT, the variator consists of two adjustable pulleys having a beltbetween them. The variator in a single cavity toroidal-type CVT has twopartially toroidal transmission discs rotating about a shaft and two ormore disc-shaped power rollers rotating on respective axes that areperpendicular to the shaft and clamped between the input and outputtransmission discs.

Embodiments of the invention disclosed here are of the spherical-typevariator utilizing spherical speed adjusters (also known as poweradjusters, balls, sphere gears or rollers) that each has a tiltable axisof rotation; the adjusters are distributed in a plane about alongitudinal axis of a CVT. The rollers are contacted on one side by aninput disc and on the other side by an output disc, one or both of whichapply a clamping contact force to the rollers for transmission oftorque. The input disc applies input torque at an input rotational speedto the rollers. As the rollers rotate about their own axes, the rollerstransmit the torque to the output disc. The input speed to output speedratio is a function of the radii of the contact points of the input andoutput discs to the axes of the rollers. Tilting the axes of the rollerswith respect to the axis of the variator adjusts the speed ratio.

SUMMARY OF INVENTION

One embodiment is a CVT. The CVT includes a central shaft and avariator. The variator includes an input disc, an output disc, aplurality of tiltable ball-leg assemblies, and an idler assembly. Theinput disc is rotatably mounted about the central shaft. Each of theplurality of tiltable ball-leg assemblies includes a ball, an axle, andat least two legs. The ball is rotatably mounted to the axle andcontacts the input disk and the output disk. The legs are configured tocontrol the tilt of the ball. The idler assembly is configured tocontrol the radial position of the legs so as to thereby control thetilt of the ball. In one embodiment, the CVT is adapted for use in abicycle.

In one embodiment, the variator includes a disk having a splined boreand a driver with splines. The splines of the driver couple to thesplined bore of the disk.

In one embodiment, a shift rod extends through the central shaft andconnects to the idler assembly. The shift rod actuates the idlerassembly.

In one embodiment, a cam loader is positioned adjacent to the input discand is configured to at least partly generate axial force and transfertorque. In one embodiment, a cam loader is positioned adjacent to theoutput disc and is configured to at least partly generate axial forceand transmit torque. In yet other embodiments, cam loaders arepositioned adjacent to both the input disc and the output disc; the camloaders are configured to at least partly generate axial force andtransmit torque.

Another embodiment is a spacer for supporting and separating a cage of aCVT having a hub shell that at least partially encloses a variator. Thespacer includes a scraper configured to scrape lubricant from a surfaceof the hub shell and direct the lubricant toward the inside of thevariator. In one embodiment, the spacer includes passages configured todirect the flow of lubricant.

Another aspect of the invention relates to a torsion disc for a CVT. Thetorsion disc includes a spline bore about its central axis, an annularrecess formed in the disc for receiving the race of a bearing, and araised surface for supporting a torsion spring.

Yet another feature of the invention concerns a shaft for supportingcertain components of a CVT. In some embodiments, the shaft has asplined flange, a central bore spanning from one end of the shaft to apoint beyond the middle of the shaft, and one or more flanges forattaching to various components of the CVT. In one embodiment, flangeson the shaft are adapted to couple to stators of the CVT.

A different aspect of the inventive CVTs relates to an axial forcegenerating system having a torsion spring coupled to a torsion disc andan input disc of the CVT. The axial force generating system may alsoinclude one or more load cam discs having ramps for energizing rollers,which are preferably located between the load cam disc and the inputdisc and/or output disc of the CVT.

Another feature of the invention is directed to an axle and axle-ballcombination for a CVT. In some embodiments, the axle includes shoulderportions and a waist portion. The axle is configured to fit in a centralbore of a traction roller of the CVT. In some embodiments, the bearingsurface between the axle and the ball may be a journal bearing, abushing, a Babbitt lining, or the axle itself. In other embodiments, theaxle and ball utilize retained bearings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of a CVT.

FIG. 2 is a partially exploded cross-sectional view of the CVT of FIG.1.

FIG. 3 is a cross-sectional view of a second embodiment of a CVT.

FIG. 4 is a partially exploded cross-sectional view of the CVT of FIG.3.

FIG. 5 a is a side view of a splined input disc driver that can be usedin a CVT.

FIG. 5 b is a front view of the disc driver of FIG. 5 a.

FIG. 6 a is a side view of a splined input disc that can be used in aCVT.

FIG. 6 b is a front view of the splined input disc of FIG. 6 a.

FIG. 7 is a cam roller disc that can be used with a CVT.

FIG. 8 is a stator that can be used with a CVT.

FIG. 9 is a perspective view of a scraping spacer that can be used witha CVT.

FIG. 10 is a cross-sectional view of a shifter assembly that can be usedin a CVT.

FIG. 11 is a perspective view of a ball-leg assembly for use in a CVT.

FIG. 12 is a perspective view of a cage that can be used in a ball-typeCVT.

FIG. 13 is a cross-sectional view of another embodiment of a CVT.

FIG. 14 is a perspective view of a bicycle hub incorporating anembodiment of a CVT.

FIG. 15 is a top elevational view of various assemblies of an embodimentof a CVT incorporated in the bicycle hub of FIG. 14.

FIG. 16 is a partially exploded, perspective view of certain assembliesof the CVT of FIG. 15.

FIG. 17 is a top elevational view of certain assemblies of the CVT ofFIG. 15.

FIG. 18 is a cross-sectional view along section A-A of the assemblies ofFIG. 17.

FIG. 19 is a perspective view of one embodiment of a shift cam assemblythat can be used with the CVT of FIG. 15.

FIG. 20 is a top elevational view of the shift cam assembly of FIG. 19.

FIG. 21 is a cross-sectional view along section B-B of the shift camassembly of FIG. 20.

FIG. 22 is perspective view of a cage assembly that can be used with theCVT of FIG. 15.

FIG. 23 is a front elevational view of the cage assembly of FIG. 22.

FIG. 24 is a right side elevational view of the cage assembly of FIG.22.

FIG. 25 is a partially exploded, front elevational view of certain axialforce generation components for the CVT of FIG. 15.

FIG. 26 is a cross-sectional view along section C-C of the CVTcomponents shown in FIG. 25.

FIG. 27 is an exploded perspective view of a mating input shaft andtorsion disc that can be used with the CVT of FIG. 15.

FIG. 28 is a perspective view of the torsion disc of FIG. 27.

FIG. 29 is a left side elevational view of the torsion disc of FIG. 28.

FIG. 30 is a front elevation view of the torsion disc of FIG. 28.

FIG. 31 is a right side elevational view of the torsion disc of FIG. 28.

FIG. 32 is a cross-sectional view along section D-D of the torsion discof FIG. 31.

FIG. 33 is a perspective view of the input shaft of FIG. 27.

FIG. 34 is a left side elevational view of the input shaft of FIG. 33.

FIG. 35 is a top side elevational view of the input shaft of FIG. 33.

FIG. 36 is a perspective view of a load cam disc that can be used withthe CVT of FIG. 15.

FIG. 37 is a top side elevational view of a ball and axle assembly thatcan be used with the CVT of FIG. 15.

FIG. 38 is a cross-sectional view along section E-E of the ball and axleassembly of FIG. 37.

FIG. 39 is a top elevational view of the bicycle hub of FIG. 14.

FIG. 40 is a cross-sectional view along section F-F of the hub of FIG.39 showing certain components of the bicycle hub of FIG. 14 and the CVTof FIG. 15.

FIG. 41 is a perspective view of a main shaft that can be used with theCVT of FIG. 15.

FIG. 42 is a top side elevational view of the main shaft of FIG. 41.

FIG. 43 is a cross-section view along section G-G of the main shaft ofFIG. 42.

FIG. 44 is a top elevational view of an alternative embodiment of a CVTthat can be used with the bicycle hub of FIG. 14.

FIG. 45 is a cross-sectional view along section H-H of the CVT of FIG.44.

FIG. 46 is a cross-sectional view of a CVT that can be used with thebicycle hub of FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The CVT embodiments described here are generally of the type disclosedin U.S. Pat. Nos. 6,241,636, 6,419,608 and 6,689,012. The entiredisclosure of each of these patents is hereby incorporated herein byreference.

FIG. 1 illustrates a spherical-type CVT 100 that can change input tooutput speed ratios. The CVT 100 has a central shaft 105 extendingthrough the center of the CVT 100 and beyond two rear dropouts 10 of theframe of a bicycle. A first cap nut 106 and second cap nut 107, eachlocated at a corresponding end of the central shaft 105, attach thecentral shaft 105 to the dropouts. Although this embodiment illustratesthe CVT 100 for use on a bicycle, the CVT 100 can be implemented on anyequipment that makes use of a transmission. For purposes of description,the central shaft 105 defines a longitudinal axis of the CVT that willserve as a reference point for describing the location and or motion ofother components of the CVT. As used here, the terms “axial,” “axially,”“lateral,” “laterally,” refer to a position or direction that is coaxialor parallel with the longitudinal axis defined by the central shaft 105.The terms “radial” and “radially” refer to locations or directions thatextend perpendicularly from the longitudinal axis.

Referring to FIGS. 1 and 2, the central shaft 105 provides radial andlateral support for a cage assembly 180, an input assembly 155 and anoutput assembly 160. In this embodiment the central shaft 105 includes abore 199 that houses a shift rod 112. As will be described later, theshift rod 112 actuates a speed ratio shift in the CVT 100.

The CVT 100 includes a variator 140. The variator 140 can be anymechanism adapted to change the ratio of input speed to output speed. Inone embodiment, the variator 140 includes an input disc 110, an outputdisc 134, tiltable ball-leg assemblies 150 and an idler assembly 125.The input disc 110 may be a disc mounted rotatably and coaxially aboutthe central shaft 105. At the radial outer edge of the input disc 110,the disc extends at an angle to a point where it terminates at a contactsurface 111. In some embodiments, the contact surface 111 can be aseparate structure, for example a ring that attaches to the input disc110, which would provide support for the contact surface 111. Thecontact surface 111 may be threaded, or press fit, into the input disc110 or it can be attached with any suitable fasteners or adhesives.

The output disc 134 can be a ring that attaches, by press fit orotherwise, to an output hub shell 138. In some embodiments, the inputdisc 110 and the output disc 134 have support structures 113 that extendradially outward from contact surfaces 111 and that provide structuralsupport to increase radial rigidity, to resist compliance of those partsunder the axial force of the CVT 100, and to allow axial forcemechanisms to move radially outward, thereby reducing the length of theCVT 100. The input disc 110 and the output disc 134 can have oil ports136, 135 to allow lubricant in the variator 140 to circulate through theCVT 100.

The hub shell 138 in some embodiments is a cylindrical tube rotatableabout the central shaft 105. The hub shell 138 has an inside that housesmost of the components of the CVT 100 and an outside adapted to connectto whatever component, equipment or vehicle uses the CVT. Here theoutside of the hub shell 138 is configured to be implemented on abicycle. However, the CVT 100 can be used in any machine where it isdesirable to adjust rotational input and output speeds.

Referring to FIGS. 1, 2, 10 and 11 a CVT may include a ball-leg assembly150 for transmitting torque from the input disc 110 to the output disc134 and varying the ratio of input speed to output speed. In someembodiments, the ball-leg assembly 150 includes a ball 101, a ball axle102, and legs 103. The axle 102 can be a generally cylindrical shaftthat extends through a bore formed through the center of the ball 101.In some embodiments, the axle 102 interfaces with the surface of thebore in the ball 101 via needle or radial bearings that align the ball101 on the axle 102. The axle 102 extends beyond the sides of the ball101 where the bore ends so that the legs 103 can actuate a shift in theposition of the ball 101. Where the axle 102 extends beyond the edge ofthe ball 101, it couples to the radial outward end of the legs 103. Thelegs 103 are radial extensions that tilt the ball axle 102.

The axle 102 passes through a bore formed in the radially outward end ofa leg 103. In some embodiments, the leg 103 has chamfers where the borefor the axle 102 passes through the legs 103, which provides for reducedstress concentration at the contact between the side of the leg 103 andthe axle 102. This reduced stress increases the capacity of the ball-legassembly 150 to absorb shifting forces and torque reaction. The leg 103can be positioned on the axle 102 by clip rings, such as e-rings, or canbe press fit onto the axle 102; however, any other type of fixationbetween the axle 102 and the leg 103 can be utilized. The ball-legassembly 150 can also include leg rollers 151, which are rollingelements attached to each end of a ball axle 102 and provide for rollingcontact of the axle 102 as it is aligned by other parts of the CVT 100.In some embodiments, the leg 103 has a cam wheel 152 at a radiallyinward end to help control the radial position of the leg 103, whichcontrols the tilt angle of the axle 102. In yet other embodiments, theleg 103 couples to a stator wheel 1105 (see FIG. 11) that allows the leg103 to be guided and supported in the stators 800 (see FIG. 8). As shownin FIG. 11, the stator wheel 1105 may be angled relative to thelongitudinal axis of the leg 103. In some embodiments, the stator wheel1105 is configured such that its central axis intersects with the centerof the ball 101.

Still referring to FIGS. 1, 2, 10 and 11, in various embodiments theinterface between the balls 101 and the axles 102 can be any of thebearings described in other embodiments below. However, the balls 101are fixed to the axles in other embodiments and rotate with the balls101. In some such embodiments, bearings (not shown) are positionedbetween the axles 102 and the legs 103 such that the transverse forcesacting on the axles 102 are reacted by the legs 103 as well as, oralternatively, the cage (described in various embodiments below). Insome such embodiments, the bearing positioned between the axles 102 andthe legs 103 are radial bearings (balls or needles), journal bearings orany other type of bearings or suitable mechanism or means.

With reference to FIGS. 1, 2, 3, 4 and 10, the idler assembly 125 willnow be described. In some embodiments, the idler assembly 125 includesan idler 126, cam discs 127, and idler bearings 129. The idler 126 is agenerally cylindrical tube. The idler 126 has a generally constant outerdiameter; however, in other embodiments the outer diameter is notconstant. The outer diameter may be smaller at the center portion thanat the ends, or may be larger at the center and smaller at the ends. Inother embodiments, the outer diameter is larger at one end than at theother and the change between the two ends may be linear or non-lineardepending on shift speed and torque requirements.

The cam discs 127 are positioned on either or both ends of the idler 126and interact with the cam wheels 152 to actuate the legs 103. The camdiscs 127 are convex in the illustrated embodiment, but can be of anyshape that produces a desired motion of the legs 103. In someembodiments, the cam discs 127 are configured such that their axialposition controls the radial position of the legs 103, which governs theangle of tilt of the axles 102.

In some embodiments, the radial inner diameter of the cam discs 127extends axially toward one another to attach one cam disc 127 to theother cam disc 127. Here, a cam extension 128 forms a cylinder about thecentral shaft 105. The cam extension 128 extends from one cam disc 127to the other cam disc 127 and is held in place there by a clip ring, anut, or some other suitable fastener. In some embodiments, one or bothof the cam discs 127 are threaded onto the cam disc extension 128 to fixthem in place. In the illustrated embodiment, the convex curve of thecam disc 127 extends axially away from the axial center of the idlerassembly 125 to a local maximum, then radially outward, and back axiallyinward toward the axial center of the idler assembly 125. This camprofile reduces binding that can occur during shifting of the idlerassembly 125 at the axial extremes. Other cam shapes can be used aswell.

In the embodiment of FIG. 1, a shift rod 112 actuates a transmissionratio shift of the CVT 100. The shift rod 112, coaxially located insidethe bore 199 of the central shaft 105, is an elongated rod having athreaded end 109 that extends out one side of the central shaft 105 andbeyond the cap nut 107. The other end of the shift rod 112 extends intothe idler assembly 125 where it contains a shift pin 114, which mountsgenerally transversely in the shift rod 112. The shift pin 114 engagesthe idler assembly 125 so that the shift rod 112 can control the axialposition of the idler assembly 125. A lead screw assembly 115 controlsthe axial position of the shift rod 112 within the central shaft 105. Insome embodiments, the lead screw assembly 125 includes a shift actuator117, which may be a pulley having a set of tether threads 118 on itsouter diameter with threads on a portion of its inner diameter to engagethe shift rod 112. The lead screw assembly 115 may be held in its axialposition on the central shaft 105 by any means, and here is held inplace by a pulley snap ring 116. The tether threads 118 engage a shifttether (not shown). In some embodiments, the shift tether is a standardshift cable, while in other embodiments the shift tether can be anytether capable of supporting tension and thereby rotating the shiftpulley 117.

Referring to FIGS. 1 and 2, the input assembly 155 allows torquetransfer into the variator 140. The input assembly 155 has a sprocket156 that converts linear motion from a chain (not shown) into rotationalmotion. Although a sprocket is used here, other embodiments of the CVT100 may use a pulley that accepts motion from a belt, for example. Thesprocket 156 transmits torque to an axial force generating mechanism,which in the illustrated embodiment is a cam loader 154 that transmitsthe torque to the input disc 110. The cam loader 154 includes a cam disc157, a load disc 158 and a set of cam rollers 159. The cam loader 154transmits torque from the sprocket 156 to the input disc 110 and alsogenerates an axial force that resolves into the contact force for theinput disc 110, the balls 101, the idler 126 and the output disc 134.The axial force is generally proportional to the amount of torqueapplied to the cam loader 154. In some embodiments, the sprocket 156applies torque to the cam disc 157 via a one-way clutch (detail notshown) that acts as a coasting mechanism when the hub 138 spins but thesprocket 156 is not supplying torque. In some embodiments, the load disc158 may be integral as a single piece with the input disc 157. In otherembodiments, the cam loader 154 may be integral with the output disc134.

In FIGS. 1 and 2, the internal components of the CVT 100 are containedwithin the hub shell 138 by an end cap 160. The end cap 160 is agenerally flat disc that attaches to the open end of the hub shell 138and has a bore through the center to allow passage of the cam disc 157,the central shaft 105 and the shift rod 112. The end cap 160 attaches tothe hub shell 138 and serves to react the axial force created by the camloader 154. The end cap 160 can be made of any material capable ofreacting the axial force such as for example, aluminum, titanium, steel,or high strength thermoplastics or thermoset plastics. The end cap 160fastens to the hub shell 138 by fasteners (not shown); however, the endcap 160 can also thread into, or can otherwise be attached to, the hubshell 138. The end cap 160 has a groove formed about a radius on itsside facing the cam loader 154 that houses a preloader 161. Thepreloader 161 can be a spring that provides and an initial clamp forceat very low torque levels. The preloader 161 can be any device capableof supplying an initial force to the cam loader 154, and thereby to theinput disc 134, such as a spring, or a resilient material like ano-ring. The preloader 161 can be a wave-spring as such springs can havehigh spring constants and maintain a high level of resiliency over theirlifetimes. Here the preloader 161 is loaded by a thrust washer 162 and athrust bearing 163 directly to the end cap 160. In this embodiment, thethrust washer 162 is a typical ring washer that covers the groove of thepreloader 161 and provides a thrust race for the thrust bearing 163. Thethrust bearing 163 may be a needle thrust bearing that has a high levelof thrust capacity, improves structural rigidity, and reduces tolerancerequirements and cost when compared to combination thrust radialbearings; however, any other type of thrust bearing or combinationbearing can be used. In certain embodiments, the thrust bearing 163 is aball thrust bearing. The axial force developed by the cam loader 154 isreacted through the thrust bearing 163 and the thrust washer 162 to theend cap 160. The end cap 160 attaches to the hub shell 138 to completethe structure of the CVT 100.

In FIGS. 1 and 2, a cam disc bearing 172 holds the cam disc 157 inradial position with respect to the central shaft 105, while an end capbearing 173 maintains the radial alignment between the cam disc 157 andthe inner diameter of the end cap 160. Here the cam disc bearing 172 andthe end cap bearing 173 are needle roller bearings; however, other typesof radial bearings can be used as well. The use of needle rollerbearings allow increased axial float and accommodates binding momentsdeveloped by the rider and the sprocket 156. In other embodiments of theCVT 100 or any other embodiment described herein, each of or either ofthe can disc bearing 172 and the end cap bearing 173 can also bereplaced by a complimentary pair of combination radial-thrust bearings.In such embodiments, the radial thrust bearings provide not only theradial support but also are capable of absorbing thrust, which can aidand at least partially unload the thrust bearing 163.

Still referring to FIGS. 1 and 2, an axle 142, being a support membermounted coaxially about the central shaft 105 and held between thecentral shaft 105 and the inner diameter of the closed end of the hubshell 138, holds the hub shell 138 in radial alignment with respect tothe central shaft 105. The axle 142 is fixed in its angular alignmentwith the central shaft 105. Here a key 144 fixes the axle 142 in itsangular alignment, but the fixation can be by any means known to thoseof skill in the relevant technology. A radial hub bearing 145 fitsbetween the axle 142 and the inner diameter of the hub shell 138 tomaintain the radial position and axial alignment of the hub shell 138.The hub bearing 145 is held in place by an encapsulating axle cap 143.The axle cap 143 is a disc having a central bore that fits aroundcentral shaft 105 and here attaches to the hub shell 138 with fasteners147. A hub thrust bearing 146 fits between the hub shell 138 and thecage 189 to maintain the axial positioning of the cage 189 and the hubshell 138.

FIGS. 3, 4 and 10 illustrate a CVT 300, which is an alternativeembodiment of the CVT 100 described above. Many of the components aresimilar between the CVT 100 embodiments described above and that of thepresent figures. Here, the angles of the input and output discs 310, 334respectively are decreased to allow for greater strength to withstandaxial forces and to reduce the overall radial diameter of the CVT 300.This embodiment shows an alternate shifting mechanism, where the leadscrew mechanism to actuate axial movement of the idler assembly 325 isformed on the shift rod 312. The lead screw assembly is a set of leadthreads 313 formed on the end of the shift rod 312 that is within ornear the idler assembly 325. One or more idler assembly pins 314 extendradially from the cam disc extensions 328 into the lead threads 313 andmove axially as the shift rod 312 rotates.

In the illustrated embodiment, the idler 326 does not have a constantouter diameter, but rather has an outer diameter that increases at theends of the idler 326. This allows the idler 326 to resist forces of theidler 326 that are developed through the dynamic contact forces andspinning contact that tend to drive the idler 326 axially away from acenter position. However, this is merely an example and the outerdiameter of the idler 326 can be varied in any manner a designer desiresin order to react the spin forces felt by the idler 326 and to aid inshifting of the CVT 300.

Referring now to FIGS. 5 a, 5 b, 6 a, and 6 b, a two part disc is madeup of a splined disc 600 and a disc driver 500. The disc driver 500 andthe splined disc 600 fit together through splines 510 formed on the discdriver 500 and a splined bore 610 formed in the splined disc 600. Thesplines 510 fit within the splined bore 610 so that the disc driver 500and the splined disc 600 form a disc for use in the CVT 100, CVT 300, orany other spherical CVT. The splined disc 600 provides for compliance inthe system to allow the variator 140, 340 to find a radial equilibriumposition so as to reduce sensitivity to manufacturing tolerances of thecomponents of a variator 140, 340.

FIG. 7 illustrates a cam disc 700 that can be used in the CVT 100, CVT300, other spherical CVTs or any other type of CVT. The cam disc 700 hascam channels 710 formed in its radial outer edge. The cam channels 710house a set of cam rollers (not shown) which in this embodiment arespheres (such as bearing balls) but can be any other shape that combineswith the shape of the cam channel 710 to convert torque into torque andaxial force components to moderate the axial force applied to thevariator 140, 340 in an amount proportional to the torque applied to theCVT. Other such shapes include cylindrical rollers, barreled rollers,asymmetrical rollers or any other shape. The material used for the camdisc channels 710 in many embodiments is preferably strong enough toresist excessive or permanent deformation at the loads that the cam disc700 will experience. Special hardening may be needed in high torqueapplications. In some embodiments, the cam disc channels 710 are made ofcarbon steel hardened to Rockwell hardness values above 40 HRC. Theefficiency of the operation of the cam loader (154 of FIG. 1, or anyother type of cam loader) can be affected by the hardness value,typically by increasing the hardness to increase the efficiency;however, high hardening can lead to brittleness in the cam loadingcomponents and can incur higher cost as well. In some embodiments, thehardness is above 50 HRC, while in other embodiments the hardness isabove 55 HRC, above 60 HRC and above 65 HRC.

FIG. 7 shows an embodiment of a conformal cam. That is, the shape of thecam channel 710 conforms to the shape of the cam rollers. Since thechannel 710 conforms to the roller, the channel 710 functions as abearing roller retainer and the requirement of a cage element isremoved. The embodiment of FIG. 7 is a single direction cam disc 700;however, the cam disc can be a bidirectional cam as in the CVT 1300 (seeFIG. 13). Eliminating the need for a bearing roller retainer simplifiesthe design of the CVT. A conformal cam channel 710 also allows thecontact stress between the bearing roller and the channel 710 to bereduced, allowing for reduced bearing roller size and/or count, or forgreater material choice flexibility.

FIG. 8 illustrates a cage disc 800 used to form the rigid supportstructure of the cage 189 of the variators 140, 340 in spherical CVTs100, 300 (and other types). The cage disc 800 is shaped to guide thelegs 103 as they move radially inward and outward during shifting. Thecage disc 800 also provides the angular alignment of the axles 102. Insome embodiments the corresponding grooves of two cage discs 800 for arespective axle 102 are offset slightly in the angular direction toreduce shift forces in the variators 140 and 340.

Legs 103 are guided by slots in the stators. Leg rollers 151 on the legs103 follow a circular profile in the stators. The leg rollers 151generally provide a translational reaction point to counteracttranslational forces imposed by shift forces or traction contact spinforces. The legs 103 as well as its respective leg rollers 151 move inplanar motion when the CVT ratio is changed and thus trace out acircular envelope which is centered about the ball 101. Since the legrollers 151 are offset from the center of the leg 103, the leg rollers151 trace out an envelope that is similarly offset. To create acompatible profile on each stator to match the planar motion of the legrollers 151, a circular cut is required that is offset from the groovecenter by the same amount that the roller is offset in each leg 103.This circular cut can be done with a rotary saw cutter; however, itrequires an individual cut at each groove. Since the cuts areindependent, there is a probability of tolerance variation from onegroove to the next in a single stator, in addition to variation betweenstators. A method to eliminate this extra machining step is to provide asingle profile that can be generated by a lath turning operation. Atoroidal-shaped lathe cut can produce this single profile in one turningoperation. The center of the toroidal cut is adjusted away from thecenter of the ball 101 position in a radial direction to compensate foroffset of the leg rollers 103.

Referring now to FIGS. 1, 9 and 12, an alternative embodiment of a cageassembly 1200 is illustrated implementing a lubrication enhancinglubricating spacer 900 for use with some CVTs where spacers 1210 supportand space apart two cage discs 1220. In the illustrated embodiment, thesupport structure for the power transmission elements, in this case thecage 389, is formed by attaching input and output side cage discs 1220to a plurality of spacers 1210, including one or more lubricatingspacers 900 with cage fasteners 1230. In this embodiment, the cagefasteners 1230 are screws but they can be any type of fastener orfastening method. The lubricating spacer 900 has a scraper 910 forscraping lubricant from the surface of the hub shell 138 and directingthat lubricant back toward the center elements of the variator 140 or340. The lubricating spacer 900 of some embodiments also has passages920 to help direct the flow of lubricant to the areas that most utilizeit. In some embodiments, a portion of the spacer 900 between thepassages 920 forms a raised wedge 925 that directs the flow of lubricanttowards the passages 920. The scraper 910 may be integral with thespacer 900 or may be separate and made of a material different from thematerial of the scraper 910, including but not limited to rubber toenhance scraping of lubricant from the hub shell 138. The ends of thespacers 1210 and the lubricating spacers 900 terminate in flange-likebases 1240 that extend perpendicularly to form a surface for mating withthe cage discs 1220. The bases 1240 of the illustrated embodiment aregenerally flat on the side facing the cage discs 1240 but are rounded onthe side facing the balls 101 so as to form the curved surface describedabove that the leg rollers 151 ride on. The bases 1240 also form thechannel in which the legs 103 ride throughout their travel.

An embodiment of a lubrication system and method will now be describedwith reference to FIGS. 3, 9, and 10. As the balls 101 spin, lubricanttends to flow toward the equators of the balls 101, and the lubricant isthen sprayed out against the hub shell 138. Some lubricant does not fallon the internal wall of the hub shell 138 having the largest diameter;however, centrifugal force makes this lubricant flow toward the largestinside diameter of the hub shell 138. The scraper 910 is positionedvertically so that it removes lubricant that accumulates on the insideof the hub shell 138. Gravity pulls the lubricant down each side ofV-shaped wedge 925 and into the passages 920. The spacer 900 is placedsuch that the inner radial end of the passages 920 end in the vicinityof the cam discs 127 and the idler 126. In this manner the idler 126 andthe cam discs 127 receive lubrication circulating in the hub shell 138.In one embodiment, the scraper 910 is sized to clear the hub shell 138by about 30 thousandths of an inch. Of course, depending on differentapplications, the clearance could be greater or smaller.

As shown in FIGS. 3 and 10, a cam disc 127 can be configured so that itsside facing the idler 226 is angled in order to receive lubricantfalling from the passages 920 and direct the lubricant toward the spacebetween the cam disc 127 and the idler 226. After lubricant flows ontothe idler 226, the lubricant flows toward the largest diameter of theidler 226, where some of the lubricant is sprayed at the axles 102. Someof the lubricant falls from the passages 920 onto the idler 226. Thislubricant lubricates the idler 226 as well as the contact patch betweenthe balls 101 and the idler 226. Due to the inclines on each side of theidler 226, some of the lubricant flows centrifugally out toward theedges of the idler 226, where it then sprays out radially.

Referring to FIGS. 1, 3 and 10, in some embodiments, lubricant sprayedfrom the idler 126, 226 towards the axle 102 falls on grooves 345, whichreceive the lubricant and pump it inside the ball 101. Some of thelubricant also falls on the contact surface 111 where the input disc 110and output disc 134 contact the balls 101. As the lubricant exits on oneside of the ball 101, the lubricant flows toward the equator of theballs 101 under centrifugal force. Some of this lubricant contacts theinput disc 110 and ball 101 contact surface 111 and then flows towardthe equator of the ball 101. Some of the lubricant flows out radiallyalong a side of the output disc 134 facing away from the balls 101. Insome embodiments, the input disc 110 and/or output disc 134 are providedwith lubrication ports 136 and 135, respectively. The lubrication ports135, 136 direct the lubrication toward the largest inside diameter ofthe hub shell 138.

FIG. 13 illustrates an embodiment of a CVT 1300 having two cam-loaders1354 that share the generation and distribution of axial force in theCVT 1300. Here, the cam loaders 1354 are positioned adjacent to theinput disc 1310 and the output disc 1334. The CVT 1300 illustrates howtorque can be supplied either via the input disc 1310 and out throughthe output disc 1334 or reversed so that torque is input through theoutput disc 1334 and output through the input disc 1310.

FIG. 14 depicts a bicycle hub 1400 configured to incorporate inventivefeatures of embodiments of the CVTs described here. Several componentsof the hub 1400 are the same as components described above; hence,further description of such components will be limited. The hub 1400includes a hub shell 138 that couples to a hub cap 1460. In someembodiments, the hub 1400 also includes an end cap 1410 that seals theend of the hub shell 138 opposite the hub cap 1460. The hub shell 138,the hub cap 1460, and the end cap 1410 are preferably made of materialsthat provide structural strength and rigidity. Such materials include,for example, steel, aluminum, magnesium, high-strength plastics, etc. Insome embodiments, depending on the specific requirements of a givenapplication of the technology, other materials might be appropriate. Forexample, the hub shell 138 may be made from composites, thermo plastics,thermoset plastics, etc.

Referring now to FIG. 14, the illustrated hub 1400 houses in itsinterior embodiments of the CVTs presented herein. A main shaft 105supports the hub 1400 and provides for attachment to the dropouts 10 ofa bicycle or other vehicle or equipment. The main shaft 105 of thisembodiment is described in further detail with reference to FIGS. 41-43.In some embodiments, as illustrated in FIGS. 15-18, a CVT 1500 includesa shifting mechanism that incorporates a rod 112 with a threaded end109. Nuts 106 and 107 lock the dropouts 10 to the main shaft 105. In theembodiment of FIG. 14, the hub 1400 includes a freewheel 1420 that isoperationally coupled to an input shaft (see FIG. 33 and FIG. 40) fortransferring a torque input into the CVT 1500. It should be noted thatalthough various embodiments and features of the CVTs described here arediscussed with reference to a bicycle application, through readilyrecognizable modifications the CVTs and features thereof can be used inany vehicle, machine or device that uses a transmission.

With reference to FIGS. 15 and 16, in one embodiment the CVT 1500 has aninput disc 1545 for transferring torque to a set of spherical tractionrollers (here shown as balls 101). FIG. 16 is a partially exploded viewof the CVT 1500. The balls 101 transfer the torque to an output disc1560. One ball 101 is illustrated in this embodiment to provide clarityin illustrating the various features of the CVT 1500, however, variousembodiments of the CVT employ anywhere from 2 to 16 balls 101 or moredepending on the torque, weight and size requirements of each particularapplication. Different embodiments use either 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16 or more balls 101. An idler 1526, mountedcoaxially about the main shaft 105, contacts and provides support forthe balls 101 and maintains their radial position about the main shaft105. The input disc 1545 of some embodiments, has lubrication ports 1590to facilitate circulation of lubricant in the CVT 1500.

Referring additionally to FIGS. 37-38, the ball 101 spins on an axle3702. Legs 103 and shift cams 1527 cooperate to function as levers thatactuate a shift in the position of the axle 3702, which shift results ina tilting of the ball 101 and, thereby, a shift in the transmissionratio as already explained above. A cage 1589 (see FIGS. 22-24) providesfor support and alignment of the legs 103 as the shift cams 1527 actuatea radial motion of the legs 103. In one embodiment, the cage includesstators 1586 and 1587 that are coupled by stator spacers 1555. In otherembodiments, other cages 180, 389, 1200 are employed.

Referring additionally to FIGS. 41-43, in the illustrated embodiment,the cage 1589 mounts coaxially and nonrotatably about the main shaft105. The stator 1586 rigidly attaches to a flange 4206 of the main shaft105 in this embodiment. An additional flange 1610 holds the stator 1587in place. A key 1606 couples the flange 1610 to the main shaft 105,which has a key seat 1608 for receiving the key 1606. Of course, theperson of ordinary skill in the relevant technology will readilyrecognize that there are many equivalent and alternative methods forcoupling the main shaft 105 to the flange 1610, or coupling the stators1586, 1587 to the flanges 1620, 4206. In certain embodiments, the mainshaft 105 includes a shoulder 4310 that serves to axially position andconstrain the flange 1610.

The end cap 1410 mounts on a radial bearing 1575, which itself mountsover the flange 1610. In one embodiment, the radial bearing 1575 is anangular contact bearing that supports loads from ground reaction andradially aligns the hub shell 138 to the main shaft 105. In someembodiments, the hub 1400 includes seals at one or both ends of the mainshaft 105. For example, here the hub 1400 has a seal 1580 at the endwhere the hub shell 138 and end cap 1410 couple together. Additionally,in order to provide an axial force preload on the output side and tomaintain axial position of the hub shell 138, the hub 1400 may includespacers 1570 and a needle thrust bearing (not shown) between the stator1587 and the radial bearing 1575. The spacers 1570 mount coaxially aboutthe flange 1610. In some embodiments, the needle thrust bearing may notused, and in such cases the radial bearing 1575 may be an angularcontact bearing adapted to handle thrust loads. The person of ordinaryskill in the relevant technology will readily recognize alternativemeans to provide the function of carrying radial and thrust loads thatthe spacers 1570, needle thrust bearing, and radial bearing provide.

Still referring to FIGS. 14, 15 and 16, in the embodiment illustrated, avariator 1500 for the hub 1400 includes an input shaft 1505 thatoperationally couples at one end to a torsion disc 1525. The other endof the input shaft 1505 operationally couples to the freewheel 1420 viaa freewheel carrier 1510. The torsion disc 1525 is configured totransfer torque to a load cam disc 1530 having ramps 3610 (see FIG. 36).The load cam disc 1530 transfers torque and axial force to a set ofrollers 2504 (see FIG. 25), which act upon a second load cam disc 1540.The input disc 1545 couples to the second load cam disc 1540 to receivetorque and axial force inputs. In some embodiments, the rollers 2504 areheld in place by a roller cage 1535.

As is well known, many traction-type CVTs utilize a clamping mechanismto prevent slippage between the balls 101 and the input disc 1545 and/oroutput disc 1560 when transmitting certain levels of torque. Provisionof a clamping mechanism is sometimes referred to here as generating anaxial force, or providing an axial force generator. The configurationdescribed above of the load cam disc 1530 acting in concert with theload cam 1540 through the rollers 2504 is one such axial forcegenerating mechanism. However, as the axial force generating device orsub-assembly generates axial force in a CVT, reaction forces are alsoproduced that are reacted in the CVT itself in some embodiments.Referring additionally to FIGS. 25 and 26, in the embodiment illustratedof the CVT 1500, the reaction forces are reacted at least in part by athrust bearing having first and second races 1602 and 1603,respectively. In the illustrated embodiment, the bearing elements arenot shown but may be balls, rollers, barreled rollers, asymmetricalrollers or any other type of rollers. Additionally, in some embodiments,one or both of the races 1602 are made of various bearing race materialssuch as steel, bearing steel, ceramic or any other material used forbearing races. The first race 1602 butts up against the torsion disc1525, and the second race 1603 butts up against the hub cap 1460. Thehub cap 1460 of the illustrated embodiment helps to absorb the reactionforces that the axial force mechanism generates. In some embodiments,axial force generation involves additionally providing preloaders, suchas one or more of an axial spring such as a wave spring 1515 or atorsion spring 2502 (see description below for FIG. 25).

Referring to FIGS. 15-18, 22-24 and 43, certain subassemblies of the CVT1500 are illustrated. The stator 1586 mounts on a shoulder 4208 of themain shaft 105 and butts up against the flange 4206 of the main shaft105. The stator 1587 mounts on a shoulder 1810 of the flange 1610. Here,screws (not shown) attach the flange 4206 to the stator 1586 and attachthe flange 1610 to the stator 1587, however, in other embodiments thestator 1587 threads onto the shoulder 1810, although the stator 1587 canbe attached by any method or means to the shoulder 1810. Because theflanges 1610 and 4206 are nonrotatably fixed to main shaft 105, the cage1589 made of the stators 1586 and 1587, among other things, attachesnonrotatably in this embodiment to the main shaft 105. The statorspacers 1555 provide additional structural strength and rigidity to thecage 1589. Additionally, the stator spacers 1555 aid in implementing theaccurate axial spacing between stators 1586 and 1587. The stators 1586and 1587 guide and support the legs 103 and axles 3702 through guidegrooves 2202.

Referring now to FIGS. 15-21, 37, 38, the ball 101 spins about the axle3702 and is in contact with an idler 1526. Bearings 1829, mountedcoaxially about the main shaft 105, support the idler 1526 in its radialposition, which bearings 1829 may be separate from or integral with theidler 1526. A shift pin 114, controlled by the shift rod 112, actuatesan axial movement of the shift cams 1527. The shift cams 1527 in turnactuate legs 103, functionally resulting in the application of a leveror pivoting action upon the axle 3702 of the ball 101. In someembodiments, the CVT 1500 includes a retainer 1804 that keeps the shiftpin 114 from interfering with the idler 1526. The retainer 1804 can be aring made of plastic, metal, or other suitable material. The retainer1804 fits between the bearings 1829 and mounts coaxially about a shiftcam extension 1528.

FIGS. 19-21 show one embodiment of the shift cams 1527 for theillustrated CVT 1500. Each shift cam disc 1572 has a profile 2110 alongwhich the legs 103 ride. Here the profile 2110 has a generally convexshape. Usually the shape of the profile 2110 is determined by thedesired motion of the legs 103, which ultimately affects the shiftperformance of the CVT 1500. Further discussion of shift cam profiles isprovided below. As shown, one of the shift cam discs 1527 has anextension 1528 that mounts about the main shaft 105. The extension 1528of the illustrated embodiment is sufficiently long to extend beyond theidler 1526 and couple to the other shift cam disc 1527. Coupling here isprovided by a slip-fit and a clip. However, in other embodiments, theshift cams 1527 can be fastened to each other by threads, screws,interference fit, or any other connection method. In some embodiments,the extension 1528 is provided as an extension from each shift cam 1527.The shift pin 114 fits in a hole 1910 that goes through the extension1528. In some embodiments, the shift cams 1527 have orifices 1920 toimprove lubrication flow through the idler bearings 1829. In someembodiments the idler bearings 1829 are press fit onto the extension1528. In such embodiments, the orifices 1920 aid in removing the idlerbearings 1829 from the extension 1528 by allowing a tool to pass throughthe shift cams 1527 and push the idler bearings 1829 off the extension1528. In certain embodiments, the idler bearings 1829 are angle contactbearings, while in other embodiments they are radial bearings or thrustbearings or any other type of bearing. Many materials are suitable formaking the shift cams 1527. For example, some embodiments utilize metalssuch as steel, aluminum, and magnesium, while other embodiments utilizeother materials, such as composites, plastics, and ceramics, whichdepend on the conditions of each specific application.

The illustrated shift cams 1527 are one embodiment of a shift camprofile 2110 having a generally convex shape. Shift cam profiles usuallyvary according to the location of the contact point between the idler1526 and the ball-leg assembly 1670 (see FIG. 16) as well as the amountof relative axial motion between the ball 101 and the idler 1526.

Referring now to the embodiment illustrated in FIGS. 16, and 18-21, theprofile of shift cams 1527 is such that axial translation of the idler1526 relative to the ball 101 is proportional to the change of the angleof the axis of the ball 101. The angle of the axis of the ball 101 isreferred to herein as “gamma.” The applicant has discovered thatcontrolling the axial translation of the idler 1526 relative to thechange in gamma influences CVT ratio control forces. For example, in theillustrated CVT 1500, if the axial translation of the idler 1526 islinearly proportional to a change in gamma, the normal force at theshift cams 1527 and ball-leg interface is generally parallel to the axle3702. This enables an efficient transfer of horizontal shift forces to ashift moment about the ball-leg assembly 1670.

A linear relation between idler translation and gamma is given as idlertranslation is the mathematical product of the radius of the balls 101,the gamma angle and RSF (i.e., idler translation=ball radius*gammaangle*RSF), where RSF is a roll-slide factor. RSF describes thetransverse creep rate between the ball 101 and the idler 126. As usedhere, “creep” is the discrete local motion of a body relative toanother. In traction drives, the transfer of power from a drivingelement to a driven element via a traction interface requires creep.Usually, creep in the direction of power transfer is referred to as“creep in the rolling direction.” Sometimes the driving and drivenelements experience creep in a direction orthogonal to the powertransfer direction, in such a case this component of creep is referredto as “transverse creep.” During CVT operation, the ball 101 and idler1526 roll on each other. When the idler is shifted axially (i.e.,orthogonal to the rolling direction), transverse creep is imposedbetween the idler 1526 and the ball 101. An RSF equal to 1.0 indicatespure rolling. At RSF values less than 1.0, the idler 1526 translatesslower than the ball 101 rotates. At RSF values greater than 1.0, theidler 1526 translates faster than the ball 101 rotates.

Still referring to the embodiments illustrated in FIGS. 16, and 18-21,the applicant has devised a process for layout of the cam profile forany variation of transverse creep and/or location of the interfacebetween the idler 1526 and the ball-leg assembly 1570. This processgenerates different cam profiles and aids in determining the effects onshift forces and shifter displacement. In one embodiment, the processinvolves the use of parametric equations to define a two-dimensionaldatum curve that has the desired cam profile. The curve is then used togenerate models of the shift cams 127. In one embodiment of the process,the parametric equations of the datum curve are as follows:theta=2*GAMMA_MAX*t−GAMMA_MAXx=LEG*sin(theta)−0.5*BALL_DIA*RSF*theta*pi/180+0.5*ARM*cos(theta)y=LEG*cos(theta)−0.5*ARM*sin(theta)z=0

The angle theta varies from minimum gamma (which in some embodiments is−20 degrees) to maximum gamma (which in some embodiments is +20degrees). GAMMA_MAX is the maximum gamma. The parametric range variable“t” varies from 0 to 1. Here “x” and “y” are the center point of the camwheel 152 (see FIG. 1). The equations for x and y are parametric. “LEG”and “ARM” define the position of the interface between the ball-legassembly 1670 and the idler 1526 and shift cams 1527. More specifically,LEG is the perpendicular distance between the axis of the ball axle 3702of a ball-leg assembly 1670 to a line that passes through the centers ofthe two corresponding cam wheels 152 of that ball-leg assembly 1570,which is parallel to the ball axle 3702. ARM is the distance betweencenters of the cam wheels 152 of a ball-leg-assembly 1670.

RSF values above zero are preferred. The CVT 100 demonstrates anapplication of RSF equal to about 1.4. Applicant discovered that an RSFof zero dramatically increases the force required to shift the CVT.Usually, RSF values above 1.0 and less than 2.5 are preferred.

Still referring to the embodiments illustrated in FIGS. 16, and 18-21,in the illustrated embodiment of a CVT 100, there is a maximum RSF for amaximum gamma angle. For example, for gamma equals to +20 degrees an RSFof about 1.6 is the maximum. RSF further depends on the size of the ball101 and the size of the idler 1526, as well as the location of the camwheel 152.

In terms of energy input to shift the CVT, the energy can be input as alarge displacement and a small force (giving a large RSF) or a smalldisplacement and a large force (giving a small RSF). For a given CVTthere is a maximum allowable shift force and there is also a maximumallowable displacement. Hence, a trade off offers designers variousdesign options to be made for any particular application. An RSF greaterthan zero reduces the required shift force by increasing the axialdisplacement necessary to achieve a desired shift ratio. A maximumdisplacement is determined by limits of the particular shiftingmechanism, such as a grip or trigger shift in some embodiments, which insome embodiments can also be affected or alternatively affected by thepackage limits for the CVT 100.

Energy per time is another factor. Shift rates for a given applicationmay require a certain level of force or displacement to achieve a shiftrate depending on the power source utilized to actuate the shiftmechanism. For example, in certain applications using an electric motorto shift the CVT, a motor having a high speed at low torque would bepreferred in some instances. Since the power source is biased towardspeed, the RSF bias would be toward displacement. In other applicationsusing hydraulic shifting, high pressure at low flow may be more suitablethan low pressure at high flow. Hence, one would choose a lower RSF tosuit the power source depending on the application.

Idler translation being linearly related to gamma is not the onlydesired relation. Hence, for example, if it is desired that the idlertranslation be linearly proportional to CVT ratio, then the RSF factoris made a function of gamma angle or CVT ratio so that the relationbetween idler position and CVT ratio is linearly proportional. This is adesirable feature for some types of control schemes.

FIGS. 22-24 show one example of a cage 1589 that can be used in the CVT1500. The illustrated cage 1589 has two stators 1586 and 1587 coupled toeach other by a set of stator spacers 1555 (only one is shown forclarity). The stator spacers 1555 in this embodiment fasten to the outerperiphery of the stators 1586 and 1587. Here screws attach the spacers1555 to the stators 1586 and 1587. However, the stators 1586 and 1587and the spacers 1555 can be configured for other means of attachment,such as press fitting, threading, or any other method or means. In someembodiments, one end of the spacers 1555 is permanently affixed to oneof the stators 1586 or 1587. In some embodiments, the spacers 1555 aremade of a material that provides structural rigidity. The stators 1586and 1587 have grooves 2202 that guide and support the legs 103 and/orthe axles 3702. In certain embodiments, the legs 103 and/or axles 3702have wheels (item 151 of FIG. 11 or equivalent of other embodiments)that ride on the grooves 2202.

FIG. 24 shows a side of the stator 1586 opposite to the grooves 2202 ofthe stator 1586. In this embodiment, holes 2204 receive the screws thatattach the stator spacers 1555 to the stator 1586. Inner holes 2210receive the screws that attach the stator 1586 to the flange 4206 of themain shaft 105. To make some embodiments of the stator 1586 lighter,material is removed from it as shown as cutouts 2206 in this embodiment.For weight considerations as well as clearance of elements of theball-leg assembly 1670, the stator 1586 may also include additionalcutouts 2208 as in this embodiment.

The embodiments of FIGS. 25, 26 and 36 will now be referenced todescribe one embodiment of an axial force generation mechanism that canbe used with the CVT 1500 of FIG. 15. FIGS. 25 and 26 are partiallyexploded views. The input shaft 1505 imparts a torque input to thetorsion disc 1525. The torsion disc 1525 couples to a load cam disc 1530that has ramps 3610. As the load cam disc 1530 rotates, the ramps 3610activate the rollers 2504, which ride up the ramps 3610 of the secondload cam disc 1540. The rollers 2504 then wedge in place, pressedbetween the ramps of the load cam discs 1530 and 1540, and transmit bothtorque and axial force from the load cam disc 1530 to the load cam disc1540. In some embodiments, the CVT 1500 includes a roller retainer 1535to ensure proper alignment of the rollers 2504. The rollers 2504 may bespherical, cylindrical, barreled, asymmetrical or other shape suitablefor a given application. In some embodiments, the rollers 2504 each haveindividual springs (not shown) attached to the roller retainer 1535 orother structure that bias the rollers 2504 up or down the ramps 3610 asmay be desired in some applications. The input disc 1545 in theillustrated embodiment is configured to couple to the load cam disc 1540and receive both the input torque and the axial force. The axial forcethen clamps the balls 101 between the input disc 1545, the output disc1560, and the idler 1526.

In the illustrated embodiment, the load cam disc 1530 is fastened to thetorsion disc 1525 with dowel pins. However, other methods of fasteningthe load cam disc 1530 to the torsion disc 1525 can be used. Moreover,in some embodiments, the load cam disc 1530 is integral with the torsiondisc 1525. In other embodiments, the torsion disc 1525 has the ramps3610 machined into it to make a single unit for transferring torque andaxial force. In the embodiment illustrated, the load cam disc 1540couples to the input disc 1545 with dowel pins. Again, any othersuitable fastening method can be used to couple the input disc 1545 tothe load cam disc 1540. In some embodiments, the input disc 1545 and theload cam disc 1540 are an integral unit, effectively as if the ramps3610 were built into the input disc 1545. In yet other embodiments, theaxial force generating mechanism may include only one set of ramps 3610.That is, one of the load cam discs 1530 or 1540 does not have the ramps3610, but rather provides a flat surface for contacting the rollers2504. Similarly, where the ramps are built into the torsion disc 1525 orthe input disc 1545, one of them may not include the ramps 3610. In loadcam discs 1530, 1540 in both embodiments having ramps on both or on onlyone disc, the ramps 3610 and the flat surface on discs without ramps canbe formed with a conformal shape conforming to the rollers 2504 surfaceshape to partially capture the rollers 2504 and to reduce the surfacestress levels.

In some embodiments, under certain conditions of operation, a preloadaxial force to the CVT 1500 is desired. By way of example, at low torqueinput it is possible for the input disc 1545 to slip on the balls 101,rather than to achieve frictional traction. In the embodimentillustrated in FIGS. 25 and 26, axial preload is accomplished in part bycoupling a torsion spring 2502 to the torsion disc 1525 and the inputdisc 1545. One end of the torsion spring 2502 fits into a hole 2930 (seeFIG. 29) of the torsion disc 1545, while the other end of the torsionspring 2502 fits into a hole of the input disc 1545. Of course, theperson of ordinary skill in the relevant technology will readilyappreciate numerous alternative ways to couple the torsion spring 2502to the input disc 1545 and the torsion disc 1525. In other embodiments,the torsion spring 2502 may couple to the roller retainer 1535 and thetorsion disc 1525 or the input disc 1545. In some embodiments where onlyone of the torsion disc 1525 or input disc 1545 has ramps 3610, thetorsion spring 2502 couples the roller retainer 1535 to the disc withthe ramps.

Still referring to the embodiments illustrated in FIGS. 15 25 and 26, asmentioned before, in some embodiments the application of axial forcesgenerates reaction forces that are reacted in the CVT 1500. In thisembodiment of the CVT 1500, a ball thrust bearing aids in managing thereaction forces by transmitting thrust between the hub cap 1460 and thetorsion disc 1525. The thrust bearing has a race 1602 that butts againstthe hub cap 1460, which in this embodiment has a recess near its innerbore for receiving the race 1602. The second race 1603 of the thrustbearing nests in a recess of the torsion disc 1525. In some embodiments,a wave spring 1515 is incorporated between the race 1602 and the hub1460 to provide axial preload. In the illustrated embodiment, a bearing2610 radially supports the hub cap 1460.

The applicant has discovered that certain configurations of the CVT 1500are better suited than others to handle a reduction in efficiency of theCVT 1500 due to a phenomenon referred to herein as bearing dragrecirculation. This phenomenon arises when a bearing is placed betweenthe torsion disc 1525 and the hub cap 1460 to handle the reaction forcesfrom axial force generation.

In some embodiments as illustrated in FIG. 1, a needle roller bearinghaving a diameter about equal to the diameter of the load cam disc 1530is used to minimize the deflection of the end cap 160. In underdrive thespeed of the torsion disc 157 (input speed) is greater than the speed ofthe end cap 160 (output speed). In underdrive the needle roller bearing(thrust bearing 163 in that embodiment) generates a drag torque oppositethe direction of rotation of the torsion disc 1525. This drag torqueacts on the torsion disc 1525 in the direction counter to the axialloading by the load cam disc 1530, and acts on the end cap 160 and thusthe hub shell 138 and output disc 134 in the direction of the outputtending to speed up the rotation of those components, these effectscombining to unload the cam loader 154 thereby reduce the amount ofaxial force in the CVT 1500. This situation could lead to slip betweenor among the input disc 110, balls 101, and/or output disc 134.

In overdrive the speed of the torsion disc 1525 is greater than thespeed of the end cap 160 and the needle bearing generates a drag torqueacting on the torsion disc 1525 in the direction of the rotation of thetorsion disc 1525 and acting on the end cap 160 against the outputrotation of the end cap 160. This results in an increase in the axialforce being generated in the CVT 1500. The increase in axial force thencauses the system to generate even more drag torque. This feedbackphenomenon between axial force and drag torque is what is referred tohere as bearing drag recirculation, which ultimately results in reducingthe efficiency of the CVT 100. Additionally, the drag torque actingagainst the end cap 160 acts as an additional drag on the output of theCVT 100 thereby further reducing its efficiency.

The applicant has discovered various systems and methods for minimizingefficiency losses due to bearing drag recirculation. As shown in FIGS.25, 26, and 40, instead of using a needle roller bearing configured asdescribed above, some embodiments the CVT 1500 employ a roller thrustbearing having races 1602 and 1603. Because the amount of drag torqueincreases with the diameter of the bearing used, the diameter of theraces 1602 and 1603 is less than the diameter of the axial forcegenerating load cam disc 1530 and in some embodiments is as small aspossible. The diameter of the races 1602 and 1603 could be 10, 20, 30,40, 50, 60, 70, 80, or 90 percent of the diameter of the load cam disc1530. In some embodiments, the diameter of the races 1602 and 1603 isbetween 30 and 70 percent of the diameter of the load cam disc 1530. Instill other embodiments, the diameter of the races 1602 and 1603 isbetween 40 and 60 percent of the diameter of the load cam disc 1530.

When a ball thrust bearing is used, in some embodiments the rollersand/or races are made of ceramic, the races are lubricated and/orsuperfinished, and/or the number of rollers is minimized whilemaintaining the desired load capacity. In some embodiments, deep grooveradial ball bearings or angular contact bearings may be used. Forcertain applications, the CVT 1500 may employ magnetic or air bearingsas means to minimize bearing drag recirculation. Other approaches toreducing the effects of bearing drag recirculation are discussed below,referencing FIG. 46, in connection with alternative embodiments of theinput shaft 1505 and the main shaft 105.

FIGS. 27-35 depict examples of certain embodiments of a torque inputshaft 1505 and a torsion disc 1525 that can be used with the CVT 1500 ofFIG. 15. The input shaft 1505 and the torsion disc 1525 couple via asplined bore 2710 on the torsion disc 1525 and a splined flange 2720 onthe input shaft 1525. In some embodiments, the input shaft 1505 and thetorsion plate 1525 are one piece, made either as a single unit (asillustrated in FIG. 1) or wherein the input shaft 1505 and the torsiondisc 1525 are coupled together by permanent attachment means, such aswelding or any other suitable adhesion process. In yet otherembodiments, the input shaft 1505 and the torsion disc 1525 areoperationally coupled through fasteners such as screws, dowel pins,clips or any other means or method. The particular configuration shownhere is preferable in circumstances where it is desired that the inputshaft 1505 and the torsion disc 1525 be separate parts, which can handlemisalignments and axial displacement due to load cam disc 1530 growthunder load, as well as uncouple twisting moments via the splined bore2710 and the splined shaft 2720. This configuration is also preferablein certain embodiments because it allows for lower manufacturingtolerances and, consequently, reduced manufacturing costs for a CVT.

Referencing FIGS. 16, 28-32, in the illustrated embodiment, the torsiondisc 1525 is generally a circular disc having an outer periphery 3110and a splined inner bore 2710. One side of the torsion disc 1525 has arecess 3205 that receives the race 1603 of a thrust bearing. The otherside of the torsion disc 1525 includes a seat 3210 and a shoulder 3220for receiving and coupling to the load cam disc 1530. The torsion disc1525 includes a raised surface 3230 that rises from the shoulder 3220,reaches a maximum height in a convex shape, and then falls toward theinner bore 2710. In one embodiment of the CVT 1500, the raised surface3230 partially supports and constrains the torsion spring 2502, while aset of dowel pins (not shown) helps to retain the torsion spring 2502 inplace. In such embodiments, the dowel pins are placed in holes 2920. Thetorsion disc 1525 shown here has three splines on its splined bore 2710.However, in other embodiments the splines can be 1, 2, 3, 4, 5, 6, 7, 8,9, 10, or more. In some embodiments, the number of splines is 2 to 7,and in others the number of splines is 3, 4, or 5.

In some embodiments, the torsion disc 1525 includes orifices 2910 forreceiving dowels that couple the torsion disc 1525 to the load cam disc1530. The torsion disc 1525 may also have orifices 2930 for receivingone end of the torsion spring 2502. In the illustrated embodiment,several orifices 2930 are present in order to accommodate differentpossible configurations of the torsion spring 2502 as well as to providefor adjustment of preload levels.

The torsion disc 1525 can be of any material of sufficient rigidity andstrength to transmit the torques and axial loads expected in a givenapplication. In some embodiments, the material choice is designed to aidin reacting the reaction forces that are generated. For example,hardened steels, steel, aluminum, magnesium, or other metals can besuitable depending on the application while in other applicationsplastics are suitable.

FIGS. 33-35 show an embodiment of an input torque shaft 1505 for usewith the CVT 1500. The torque input shaft 1505 consists of a hollow,cylindrical body having a splined flange 2720 at one end and a key seat3310 at the other end. In this embodiment, the key seat 3310 receives akey (not shown) that operationally couples the input shaft 1505 to afreewheel carrier 1510 (see FIGS. 14, 15), which itself couples to thefreewheel 1420. The surfaces 2720 and 3410 are shaped to mate with thesplined bore 2710 of the torsion disc 1525. Thus, concave surfaces 2720of some embodiments will preferably be equal in number to the splines inthe splined bore 2710. In some embodiments, the concave surfaces 2720may number 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more. In some embodiments,the concave surfaces 2720 number 2 to 7, and in others there are 3, 4,or 5 concave surfaces 2720.

As shown, the input shaft 1505 has several clip grooves that help inretaining various components, such as bearings, spacers, etc., in placeaxially. The input shaft 1505 is made of a material that can transferthe torques expected in a given application. In some instances, theinput shaft 1505 is made of hardened steel, steel, or alloys of othermetals while in other embodiments it is made of aluminum, magnesium orany plastic or composite or other suitable material.

FIG. 36 shows an embodiment of a load cam disc 1540 (alternately 1530)that can be used with the CVT 1500. The disc 1540 is generally acircular ring having a band at its outer periphery. The band is made oframps 3610. Some of the ramps 3610 have holes 3620 that receive dowelpins (not shown) for coupling the load cam disc 1530 to the torsion disc1525 or the load cam disc 1540 to the input disc 1545. In someembodiments, the ramps 3610 are machined as a single unit with the loadcam discs 1530, 1540. In other embodiments, the ramps 3610 may beseparate from a ring substrate (not shown) and are coupled to it via anyknown fixation method. In the latter instance, the ramps 3610 and thering substrate can be made of different materials and by differentmachining or forging methods. The load cam disc 1540 can be made, forexample, of metals or composites.

Referencing FIG. 37 and FIG. 38, an embodiment of an axle 3702 consistsof an elongated cylindrical body having two shoulders 3704 and a waist3806. The shoulders 3704 begin at a point beyond the midpoint of thecylindrical body and extend beyond the bore of the ball 101. Theshoulders 3704 of the illustrated embodiment are chamfered, which helpsin preventing excessive wear of the bushing 3802 and reduces stressconcentration. The ends of the axle 3702 are configured to couple tobearings or other means for interfacing with the legs 103. In someembodiments, the shoulders 3704 improve assembly of the ball-legassembly 1670 by providing a support, stop, and/or tolerance referencepoint for the leg 103. The waist 3806 in certain embodiments serves asan oil reservoir. In this embodiment, a bushing 3802 envelops the axle3702 inside the bore of the ball 101. In other embodiments, bearings areused instead of the bushing 3802. In those embodiments, the waist 3806ends where the bearings fit inside the ball 101. The bearings can beroller bearings, drawn cup needle rollers, caged needle rollers, journalbearings, or bushings. In some embodiments, it is preferred that thebearings are caged needle bearings or other retained bearings. Inattempting to utilize general friction bearings, the CVT 100, 1500 oftenfails or seizes due to a migration of the bearings or rolling elementsof the bearings along the axles 3702, 102 out of the balls 101 to apoint where they interfere with the legs 103 and seize the balls 101. Itis believed that this migration is caused by force or strain wavesdistributed through the balls 101 during operation. Extensive testingand design has lead to this understanding and the Applicant's believethat the use of caged needle rollers or other retained bearingssignificantly and unexpectedly lead to longer life and improveddurability of certain embodiments of the CVT 100, 1500. Embodimentsutilizing bushings and journal material also aid in the reduction offailures due to this phenomenon. The bushing 3802 can be replaced by,for example, a babbitt lining that coats either or both of the ball 101or axle 3702. In yet other embodiments, the axle 3702 is made of bronzeand provides a bearing surface for the ball 101 without the need forbearings, bushing, or other linings. In some embodiments, the ball 101is supported by caged needle bearings separated by a spacer (not shown)located in the middle portion of the bore of the ball 101. Additionally,in other embodiments, spacers mount on the shoulders 3704 and separatethe caged needle bearings from components of the leg 103. The axle 3702can be made of steel, aluminum, magnesium, bronze, or any other metal oralloy. In certain embodiments, the axle 3702 is made of plastic orceramic materials.

One embodiment of the main shaft 105 is depicted in FIGS. 41-43. Themain shaft 105 is an elongated body having an inner bore 4305 forreceiving a shift rod 112 (see FIGS. 16 and 40). As implemented in theCVT 1500, the main shaft 105 is a single piece axle that providessupport for many of the components of the CVT 1500. In embodiments wherea single piece axle is utilized for the main shaft 105, the main shaft105 reduces or eliminates tolerance stacks in certain embodiments of theCVT 1500. Furthermore, as compared with multiple piece axles, the singlepiece main shaft 105 provides greater rigidity and stability to the CVT1500.

The main shaft 105 also includes a through slot 4204 that receives andallows the shift pin 114 to move axially, that is, along thelongitudinal axis of the main shaft 105. The size of the slots 4204 canbe chosen to provide shift stops for selectively determining a ratiorange for a given application of the CVT 1500. For example, a CVT 1500can be configured to have a greater underdrive range than overdriverange, or vice-versa, by choosing the appropriate dimension and/orlocation of the slots 4204. By way of example, if the slot 4204 shown inFIG. 42 is assumed to provide for the full shift range that the CVT 1500is capable of, a slot shorter than the slot 4204 would reduce the ratiorange. If the slot 4204 were to be shortened on the right side of FIG.42, the underdrive range would be reduced. Conversely, if the slot 4204were to be shortened on the left side of FIG. 42, the overdrive rangewould be reduced.

In this embodiment, a flange 4206 and a shoulder 4208 extend from themain shaft 105 in the radial direction. As already described, the flange4206 and the shoulder 4208 facilitate the fixation of the stator 1586 tothe main shaft 105. In some embodiments, the bore of the stator 1586 issized to mount to the main shaft 105 such that the shoulder 4208 can bedispensed with. In other embodiments, the shoulder 4208 and/or theflange 4206 can be a separate part from the main shaft 105. In thoseinstances, the shoulder 4208 and/or flange 4206 mount coaxially aboutthe main shaft 105 and affix to it by any well known means in therelevant technology. In the embodiment depicted, the main shaft 105includes a key seat 4202 for receiving a key 1606 that rotationallyfixes the flange 1610 (see FIG. 16). The key 1606 may be a woodruff key.The main shaft 105 of some embodiments is made of a metal suitable interms of manufacturability, cost, strength, and rigidity. For example,the main shaft can be made of steel, magnesium, aluminum or other metalsor alloys.

The operation of the hub 1400 having one embodiment of the CVT 1500described above will now be described with particular reference to FIGS.39 and 40. The freewheel 1420 receives torque from a bicycle chain (notshown). Since the freewheel 1420 is fixed to the freewheel carrier 1510,the freewheel 1420 imparts the torque to the freewheel carrier 1510,which in turns transmits the torque to the input shaft 1505 via a keycoupling (not shown). The input shaft 1505, riding on needle bearings4010 and 4020 mounted on the main shaft 105, inputs the torque to thetorsion disc 1525 via the splined bore 2710 and splined surfaces 2720and 3410 of the input shaft 1505. Needle bearing 4010 is preferablyplaced near or underneath the freewheel carrier 1510 and/or freewheel1420. This placement provides appropriate support to the input shaft1505 to prevent transmission of radial loading from the freewheelcarrier 1510 as a bending load through the CVT 1400. Additionally, insome embodiments a spacer 4030 is provided between the needle bearings4010 and 4020. The spacer 4030 may be made of, for example, Teflon.

As the torsion disc 1525 rotates, the load cam disc 1530 coupled to thetorsion disc 1525 follows the rotation and, consequently, the ramps 3610energize the rollers 2504. The rollers 2504 ride up the ramps 3610 ofthe load cam disc 1540 and become wedged between the load cam disc 1530and the load cam disc 1540. The wedging of the rollers 2504 results in atransfer of both torque and axial force from the load cam disc 1530 tothe load cam disc 1540. The roller cage 1535 serves to retain therollers 2504 in proper alignment.

Because the load cam disc 1540 is rigidly coupled to the input disc1545, the load cam disc 1540 transfers both axial force and torque tothe input disc 1545, which then imparts the axial force and torque tothe balls 101 via frictional contact. As the input disc 1545 rotatesunder the torque it receives from the load cam disc 1540, the frictionalcontact between the input disc 1545 and the balls 101 forces the balls101 to spin about the axles 3702. In this embodiment, the axles 3702 areconstrained from rotating with the balls 101 about their ownlongitudinal axis; however, the axles 3702 can pivot or tilt about thecenter of the balls 101, as in during shifting.

The input disc 1545, output disc 1560, and idler 1526 are in frictionalcontact with the balls 101. As the balls 101 spin on the axles 3702, theballs 101 impart a torque to the output disc 1560, forcing the outputdisc 1560 to rotate about the shaft 105. Because the output disc 1560 iscoupled rigidly to the hub shell 138, the output disc 1560 imparts theoutput torque to the hub shell 138. The hub shell 138 is mountedcoaxially and rotatably about the main shaft 105. The hub shell 138 thentransmits the output torque to the wheel of the bicycle via well knownmethods such as spokes.

Still referring to FIGS. 39 and 40, shifting of the ratio of input speedto output speed, and consequently a shift in the ratio of input torqueto output torque, is accomplished by tilting the rotational axis of theballs 101, which requires actuating a shift in the angle of the axles3702. A shift in the transmission ratio involves actuating an axialmovement of the shift rod 112 in the main shaft 105, or in rotation ofthe shift rod 312 of FIG. 3. The shift rod 112 translates axially thepin 114, which is in contact with the shift cams 1527 via the bore 1910in the extension 1528. The axial movement of the shift pin 114 causes acorresponding axial movement of the shift cams 1527. Because the shiftcams 1527 engage the legs 103 (via cam wheels 152, for example), thelegs 103 move radially as the legs 103 move along the shift cam profile2110. Since the legs 103 are connected to the axles 3702, the legs 103act as levers that pivot the axles 3702 about the center of the balls101. The pivoting of the axles 3702 causes the balls 101 to change axisof rotation and, consequently, produce a ratio shift in thetransmission.

FIG. 44 and FIG. 45 show an embodiment of a CVT 4400 having an axialforce generating mechanism that includes one load cam disc 4440 actingon the input disc 1545 and another load cam disc 4420 acting on theoutput disc 1560. In this embodiment, the load cam discs 4440 and 4420incorporate ramps such as ramps 3610 of the load cam discs 1530 and1540. In this embodiment, neither of the input disc 1545 or the outputdisc 1560 has ramps or is coupled to discs with ramps. However, in otherembodiments, it may be desirable to provide one or both of the inputdisc 1545 or output disc 1560 with discs having ramps, or building theramps into the input disc 1545 and/or output disc 1560 to cooperate withthe load cam discs 4420, 4440. The CVT 4400 of some embodiments furtherincludes a roller retainer 4430 to house and align a set of rollers (notshown) that is between the load cam disc 4420 and the output disc 1560.In the embodiment shown, the roller retainer 4430 radially pilots on theoutput disc 1560. Similarly, there is a roller retainer 4410 between theload cam disc 4440 and the input disc 1545. The rollers and discsdescribed with reference to these embodiments can be of any type orshape as described above for previous axial force generating devices. Insome embodiments the angles of the ramps incline from the surface of thedisc at an angle that is (or is between) 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15 degrees or more or any portion between any of these.

FIG. 46 illustrates an embodiment of a CVT 1600 having an input shaft4605 and a main shaft 4625 adapted to decrease bearing dragrecirculation effects. The CVT 100 includes an axial force generator 165which generates an axial force that is reacted in part by a needleroller bearing 4620. A hub cap 4660 reacts drag torque and axial forcesfrom the needle roller bearing 4620. In other embodiments, the needleroller bearing 4620 is replaced by a ball thrust bearing and in otherembodiments the ball thrust bearing has a diameter smaller than thediameter of the needle roller bearing 4620.

In this embodiment, the main shaft 4625 has a shoulder 4650 thatprovides a reaction surface for a washer 4615, which can also be a clip,for example (all of which are integral in some embodiments). The inputshaft 4605 is fitted with an extension 1410 that reacts against abearing 4645. The bearing 4645 can be a thrust bearing. As shown, theinput shaft 4605 and driver disc (similar to the torsion disc 1525) area single piece. However, in other embodiments the input shaft 4605 maybe coupled to a torsion disc 1525, for example, by threading, keying, orother fastening means. In the illustrated embodiment, some of thereaction force arising from the generation of axial force is reacted tothe main shaft 4625, thereby reducing bearing drag recirculation. In yetanother embodiment (not shown), the extension 1410 is reacted againstangular thrust bearings that also support the input shaft 4605 on themain shaft 4625. In this latter embodiment, the shoulder 4650 and washer4615 are not required. Rather, the main shaft 4625 would be adapted tosupport and retain the angular thrust bearings.

In many embodiments described herein, lubricating fluids are utilized toreduce friction of the bearings supporting many of the elementsdescribed. Furthermore, some embodiments benefit from fluids thatprovide a higher coefficient of traction to the traction componentstransmitting torque through the transmissions. Such fluids, referred toas “traction fluids” suitable for use in certain embodiments includecommercially available Santotrac 50, 5CST AF from Ashland oil, OS#155378from Lubrizol, IVT Fluid #SL-2003B21-A from Exxon Mobile as well as anyother suitable lubricant. In some embodiments the traction fluid for thetorque transmitting components is separate from the lubricant thatlubricates the bearings.

The foregoing description details certain embodiments of the invention.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the invention can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the inventionshould not be taken to imply that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated. The scope of the invention should therefore be construed inaccordance with the appended claims and any equivalents thereof.

1. A system for generating axial force in a continuously variabletransmission (“CVT”) having a central shaft, the system comprising: atorsion spring mounted coaxially about the central shaft of the CVT; atorsion disc coupled to the torsion spring, the torsion disc adapted topartially constrain the torsion spring; a first load cam disc having aplurality of ramps, the first load cam disc operationally coupled to thetorsion disc; and a plurality of rollers configured to be energized bythe first load cam disc.
 2. The system of claim 1, further comprising asecond load cam disc having a plurality of ramps, the second load camdisc configured to transmit axial force received from the plurality ofrollers.
 3. The system of claim 1, wherein the torsion disc comprises ashoulder for receiving and supporting the first load cam disc.
 4. Thesystem of claim 2, wherein the torsion disc comprises a recess forreceiving and supporting a bearing.
 5. (canceled)
 6. The system of claim2, wherein the torsion disc comprises a splined bore.
 7. (canceled) 8.(canceled)
 9. (canceled)
 10. (canceled)
 11. The system of claim 2,wherein the first load cam disc and the second load cam disc eachcomprises helical ramps.
 12. The system of claim 2, wherein the torsionspring couples to an input disc of the CVT.
 13. A system for generatingaxial force in a continuously variable transmission (CVT) having acentral shaft, the system comprising: a torsion spring means mountedcoaxially about the central shaft of the CVT; a torsion disc meanscoupled to the torsion spring means, the torsion disc adapted topartially constrain the torsion spring means; a first load cam discmeans having a plurality of ramps, the first load cam disc meansoperationally coupled to the torsion disc; and a plurality of rollermeans configured to be energized by the first load cam disc means. 14.The system of claim 13, further comprising a second load cam disc meanshaving a plurality of ramps, the second load cam disc means configuredto transmit axial force received from the plurality of rollers.
 15. Thesystem of claim 13, wherein the torsion disc means comprises a shoulderfor receiving and supporting the first load cam disc.
 16. The system ofclaim 14, wherein the torsion disc means comprises a recess forreceiving and supporting a bearing.
 17. (canceled)
 18. The system ofclaim 13, wherein the torsion disc means comprises a splined bore. 19.(canceled)
 20. (canceled)
 21. (canceled)
 22. (canceled)
 23. The systemof claim 14, wherein the first load cam disc means and the second loadcam disc means each comprises helical ramps.
 24. (canceled)
 25. A methodof manufacturing a system for generating axial force in a continuouslyvariable transmission (CVT) having a central shaft, the methodcomprising: mounting a torsion spring coaxially about the central shaftof the CVT; coupling a torsion disc to the torsion spring, the torsiondisc adapted to partially constrain the torsion spring; forming a firstload cam disc having a plurality of ramps, the first load cam discoperationally coupled to the torsion disc; and configuring a pluralityof rollers to be energized by the first load cam disc.
 26. The method ofclaim 25, further comprising the step of a second load cam disc having aplurality of ramps, the second load cam disc configured to transmitaxial force received from the plurality of rollers.
 27. The method ofclaim 25, wherein the torsion disc comprises a shoulder for receivingand supporting the first load cam disc.
 28. The method of claim 26,wherein the torsion disc comprises a recess for receiving and supportinga bearing.
 29. (canceled)
 30. The method of claim 25, wherein thetorsion disc comprises a splined bore.
 31. (canceled)
 32. (canceled) 33.(canceled)
 34. (canceled)
 35. The method of claim 26, wherein the firstload cam disc and the second load cam disc each comprises helical ramps.36. The method of claim 26, wherein the torsion spring couples to aninput disc of the CVT.
 37. A system for generating axial force in acontinuously variable transmission (CVT), the system comprising: aninput disc; an output disc; a plurality of traction rollers disposedbetween the input disc and the output disc; a first load cam disc havinga plurality of ramps; a first set of rollers, disposed between the firstload cam disc and the input disc, adapted to be energized by the firstload cam disc, and configured to transmit axial force to the input disc;a second load cam disc having a plurality of ramps; a second set ofrollers, disposed between the second load cam disc and the output disc,adapted to be energized by the second load cam disc, and configured totransmit axial force to the output disc.
 38. (canceled)
 39. (canceled)40. (canceled)
 41. The system of claim 37, wherein the input disccomprises ramps configured to be in frictional contact with the firstset of rollers.
 42. The system of claim 37, wherein the output disccomprises ramps configured to be in frictional contact with the secondset of rollers.
 43. The system of claim 37, further comprising a torsionspring coupling the first load cam disc and the input disc. 44.(canceled)
 45. The system of claim 37, wherein the first load cam disccouples to a torsion disc of the CVT.